This invention relates to water-soluble polyamine adducts, compositions thereof with epoxy resins and methods for making the same, and more particularly to water-soluble curing agents in the form of an aqueous solution of polyamine adducts with epoxy resins.
Most organic solvents are ecologically unfriendly and damaging for the environment. Attempts were made to at least partially replace the organic solvents by water. Most water-based curing agents for epoxy resins have drawbacks such as relatively long hardening time, poor stability on green concrete, and a breakdown of a curing agente/poxy resins emulsion after it is added to a concrete. In addition, the known curing agents can only be applied in thin films. Furthermore, the chemical resistance of these curing agents is not as good as that of solvent-based or solvent-free epoxy systems.
It is known to use exchange chemistry for production of amino functional phenols, which are generally referred to as Mannich bases. The preparation of Mannich bases is further described in “Advances in Chemistry of Mannich bases” by M. Tramontini, Methods in Synthetic Organic Chemistry-Synthesis, Academic Press, pp. 703-775, 1973; “Mannich Bases in Polymer Chemistry” by M. Tramontini et al., Polymer, 1988, vol. 29, May, pp. 771-788; and “The Mannich Reaction” by F. F. Blick, Org. Reactions 10, 303 (1942).
It is known to use Mannich bases as curing agents for epoxy resins, e.g., as disclosed in U.S. Pat. No. 4,269,742 to Goeke et al. This patent describes making Mannich bases by a trans-aminification reaction or exchange chemistry, wherein a higher boiling amine such as amidoamine or polyamidoamine displaces a lower boiling amine. This patent does not describe subsequent adduction or modification of curing agents for waterborne formulations.
U.S. Pat. No. 4,736,011 to Waddill et al. describes Mannich condensates, which are prepared by the reaction of an imidazole with formaldehyde and a polyoxyalkylene polyamine.
U.S. Pat. No. 3,734,965 to Becker describes the preparation of phenolic resins by condensation of a polyoxypropylene polyamine with a phenol and an aldehyde.
U.S. Pat. No. 4,714,750 to Grigsby et al. describes Mannich condensation of 2,6-di-t-butyl-phenol with formaldehyde and polyoxyalkylene amine. Similarly, U.S. Pat. No. 5,098,986 to Speranza et al. describes a two-stage reaction, where during the first stage an alkylphenol undergoes a reaction with formaldehyde and a first polyoxyalkylene diamine to form a condensate. During the second stage, the resulting condensate is further reacted with formaldehyde and a second polyoxyalkylene diamine.
More recently, other patents disclosed the use of some Mannich base condensates as emulsions in waterborne epoxy applications. U.S. Pat. No. 5,120,817 to Speranza et al. describes an epoxy resin composition containing a Mannich condensate as a curing agent, wherein the Mannich condensate is a polyoxyethylenediamine formed by condensation of phenol, formaldehyde and a polyoxyethylenediamine. The polyoxyethylenediamine has the following formula:NH2(CH2CH2O)x—CH2CH2NH2wherein x ranges from 1 to 3. When phenol, formaldehyde and polyoxyethylenediamine were reacted in a ratio of 1:3:3, the resulting reaction mixture gelled and was therefore unusable as the curing agent (See column 6, lines 50-53).
Japanese Patent 10101774 describes a composition containing a polyepoxide and a Mannich base polyamine prepared by reacting a phenolic compound with a carbonyl compound and a polyamine. The resulting Mannich base polyamine is further reacted with a diepoxide having an aromatic or alicyclic structure in the molecule and two glycidyl groups, e.g., a diglycidyl ether of polyoxyethylene glycol.
In addition, water-based solutions of polyamine adducts tend to become cloudy as can be observed by a human eye upon dilution with water, and thereby, they are not capable of maintaining a single phase uniformity required for further application of the solution.
In making concrete structures such as floors, it is known to apply to a wet concrete substrate a substance that is designed to retard the evaporation of water from the concrete substrate. Such substances are referred to in the industry as curing compounds. In prior art, curing compound (wax) is sprayed on concrete to slow down evaporation of water. After the concrete substrate has cured, it is necessary to remove the curing compound from the concrete substrate prior to applying primer or another coating. Therefore, curing concrete results in a sequence of multiple steps that is costly and time consuming. p Further, it is known in the prior art that when coatings are made with epoxy curing agents and applied to green concrete, such coatings suffer from poor adhesion to the concrete. It is also found that application of water-born epoxy curing agents often results in breaking of the emulsion. Often it is necessary for concrete to be cured for a period of up to one month before a coating can be applied to have adequate adhesion.
There is a need to provide a curing compound, which can also serve as a primer and does not have to be removed.
Further, there is a need to provide epoxy curing agents with good adhesive properties that can be formulated with epoxy resins to provide coatings for less than fully cured concrete, i.e., green concrete.
It is further desired to provide a water-soluble curing agent for epoxy applications, which maintain a single phase when diluted with water to low concentrations. It is desired to overcome the above drawbacks and to find products with improved properties. It is further desired to provide an amine-based epoxy resin curing composition, which is soluble in water and can easily emulsify liquid epoxy resins. It is still further desired to improve the stability of systems comprising concrete for a variety of applications such as a polymer modified concrete, a primer on green concrete, and a concrete curing compound.
All references cited herein are incorporated herein by reference in their entireties.